If you're applying this year, all you can do is to focus on doing the best job you can on the applications. You can't change your candidacy in a few months (think about it - what can you really do in 2-3 months to change how they see the 10+ years of adult life? At most, what you do will only have an incremental effect, and it won't fundamentally change who you are).
The one thing to keep in mind is that you have the typical mentality of an engineer who focuses way too much on the numbers (GMAT/GPA) - your GMAT isn't what gets you in. A low one can keep you out (low meaning below mid-600s), but beyond that, it's not going to make or break. In short, you can score an 800 and it still won't change your candidacy. From your post, it's clear you have the analytical horsepower (that's what engineers are for), but what's not clear is whether you are well-rounded enough or have the interpersonal skills and leadership potential to be a good manager - this is the one aspect where engineers like yourself have a much harder time convincing the adcom, and it's the one major area that is of greater concern than your numbers.
Alex Chu
alex@mbaapply.com
www.mbaapply.com
http://mbaapply.blogspot.com